Electro-mechanical brake

ABSTRACT

Provided is an electro-mechanical brake (EMB) including a driving unit configured to generate rotational force by power selectively applied as a user operates a brake pedal, a differential gear unit including a first shaft and a second shaft disposed to be aligned to form rotational shafts and rotate in the same direction by rotational force from the driving unit, a first pad disposed on one side of a brake disk, a second pad disposed on the other side of the disk, a first braking unit configured to enable the first pad to be brought into contact with one side of the disk according to a rotation of the first shaft to generate braking force, and a second braking unit configured to enable the second pad to be brought into contact with the other side of the disk according to a rotation of the second shaft to generate braking force.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. §119 to Korean PatentApplication No. 10-2014-0069211, filed on Jun. 9, 2014, the disclosureof which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention relates to an electro-mechanical brake and, moreparticularly, to an electro-mechanical brake that generates brakingforce of a rotary disk by an electric driving unit.

BACKGROUND

In general, a brake is known to serve to convert kinetic energy of arunning vehicle into thermal energy by mechanical friction of a frictionmaterial and dissipate the converted thermal energy in the air anddecelerate or stop the vehicle.

In a driving scheme of generating mechanical friction, a hydrauliccaliper including a hydraulic cylinder and a piston is largely used invehicles, and here, force applied to step on a brake pedal by a driveris amplified by a hydraulic booster, and the amplified hydraulicpressure is delivered to a hydraulic caliper (having a large sectionalarea) installed in each wheel through a master cylinder (having a smallsectional area) and an oil pipe.

Consequently, force equivalent to the product of hydraulic pressuredelivered to a slave cylinder of the caliper and the sectional area ofthe caliper cylinder pushes the piston, and the piston moves pads towarda disk to make the pads brought into contact with the disk, andsubsequently generates great clamping force.

Eventually, force equivalent to the product of the clamping force and acoefficient of friction of a contact surface of the disk exerts asbraking force on the disk, and resultantly, small pedal force isconverted into great clamping force so as to be used to perform braking.

Types of hydraulic disk brake systems are classified as a floating typedisk brake system, a fixed caliper type disk brake system, and afloating caliper type disk brake system.

Thereamong, the floating caliper type disk brake system is commonlyused.

The floating caliper type brake system has a structure in which ahydraulic piston pressing unit moves one inner pad to a disk and makethe pad clamped to the disk and a caliper housing slides in the oppositedirection of the movement of the inner pad by reaction force since thento pull an outer pad toward the disk to clamp both sides of the rotarydisk to brake the disk.

Since the floating caliper type brake system has a small number ofcomponents, is light in weight, and has an excellent cooling operation,the floating caliper type brake system is used in most automobiles.However, at an initial braking stage, since the inner pad is firstclamped all the time and the outer pad is subsequently operated uponreceiving the reaction force, wear variations may be generated.

Also, until before the outer pad is clamped, braking force at theinitial braking operation is inadequate.

In line with an alteration to hybrid, fuel cell, electric vehicles asfuture automobiles and demand for vehicle safety andenvironment-friendliness, the necessity for electro-mechanical brake(EMB) employing an electric motor, in the place of an existing hydraulicbrake, to brake wheels has emerged, for which, thus, various EMBproducts have been developed.

Referring to a structure of an EMB product, it has a mechanism,eliminating a hydraulic driving unit (hydraulic cylinder or piston) forpressing pads in an existing hydraulic disk brake, a motor driving unit(a motor, a roller screw, a decelerator, etc.) is used instead and arotary disk is braked by using a motor as a power source.

This mechanism is similar to that of a floating caliper type of ahydraulic disk brake.

Namely, using a motor as a power source, an inner pad is first moved andclamped, and a sliding caliper is moved by reaction force since then, toclamp an outer pad, thus performing braking.

Thus, the related art EMB product still involves the generation of wearvariations between the inner pad and the outer pad, namely, theshortcomings of the floating caliper type remain unsolved, and due tothe operational principle (after the inner pad is moved and clamped, thecaliper is moved by reaction force to clamp the outer pad), it takesmore time to reach required braking force, compared with a fixed type,degrading responsiveness.

SUMMARY

Accordingly, the present invention provides an electro-mechanical brakein which pads disposed on both sides of a disk are substantiallysimultaneously clamped to the disk to minimize wear variations betweenboth sides of the disk and enhance responsiveness in a brake operation.

In one general aspect, an electro-mechanical brake (EMB) includes: adriving unit configured to generate rotational force by powerselectively applied as a user operates a brake pedal; a differentialgear unit connected to the driving unit and including a first shaft anda second shaft disposed to be aligned to form rotational shafts androtate in the same direction by rotational force from the driving unit;a first pad disposed on one side of a brake disk; a second pad disposedon the other side of the disk; a first braking unit connected to thefirst shaft in one end thereof and connected to the first pad in theother end thereof and configured to enable the first pad to be broughtinto contact with one side of the disk according to a rotation of thefirst shaft to generate braking force; and a second braking unitconnected to the second shaft in one end thereof and connected to thesecond pad in the other end thereof and configured to enable the secondpad to be brought into contact with the other side of the disk accordingto a rotation of the second shaft to generate braking force.

The driving unit may be configured as a driving motor having a drivinggear coupled to a rotational shaft, and the differential gear unit mayinclude: a ring gear rotated in mesh with the driving gear; adifferential case coupled to one side of the ring gear and rotatedtogether with the ring gear; a first shaft penetrating through thedifferential case; a second shaft penetrating through the ring gear andaligned with the first shaft; a pair of side gears disposed to face eachother and coupled to one end of the first shaft and the other end of thesecond shaft, respectively, within the differential case; a pair ofdifferential pinions engaged with the pair of side gears perpendicularlyand disposed to face each other within the differential case; and afirst driven gear coupled to one end of the second shaft, wherein whenthe driving motor rotates, the first shaft and the second shaft arerotated in the same direction according to rotations of the ring gearand the differential case.

The first braking unit may be disposed in a direction parallel to thefirst shaft and varied in length in a length direction of the firstshaft according to a rotation of the first shaft, and the second brakingunit may be disposed in a direction parallel to the second shaft andvaried in length in a length direction of the second shaft according toa rotation of the second shaft.

The first braking unit may include a first screw unit connected to thefirst shaft in one end thereof and having a thread formed on an outercircumferential surface of the other end thereof; and a first nut unitscrew-coupled to the first screw unit and connected to the first pad,wherein the first pad coupled to the first nut unit linearly moves in adirection toward the disk according to a rotation of the first screwunit by the first shaft.

The second braking unit may include: a second driven gear engaged withthe first driven gear coupled to the second shaft so as to be connectedto the second shaft; a second screw unit coupled to the second drivengear in one end thereof and having a thread formed on an outercircumferential surface of the other end thereof; and a second nut unitscrew-coupled to the second screw unit and connected to the second padby a caliper, wherein the second pad coupled to the second nut unitlinearly moves in a direction toward the disk according to a rotation ofthe second screw unit by the second shaft.

The first braking unit, with a length increasing, may move the first padin the direction toward the disk, and the second braking unit, with alength decreasing, may move the second pad in the direction toward thedisk.

The first pad and the second pad may simultaneously be brought intocontact with the disk according to operations of the first braking unitand the second braking unit based on a rotation of the differential gearunit.

The threads of the first screw unit and the second screw unit may beformed in the same direction.

A direction change gear may be disposed between the first driven gearand the second driven gear, and the threads of the first screw unit andthe second screw unit may be formed in the opposite directions.

Other features and aspects will be apparent from the following detaileddescription, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an electro-mechanical brake (EMB)according to an embodiment of the present invention.

FIG. 2 is a plan view of the EMB according to an embodiment of thepresent invention.

FIG. 3 is an exploded perspective view of the EMB according to anembodiment of the present invention.

FIG. 4 is a perspective view of a differential gear unit of the EMBaccording to an embodiment of the present invention.

FIG. 5 is a cross-sectional view taken along line A-A′ of FIG. 1.

FIG. 6 is a cross-sectional view illustrating a state in which a firstbraking unit and a second braking unit are operated by a driving unit inFIG. 5.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention will be described indetail with reference to the accompanying drawings.

FIG. 1 is a perspective view of an electro-mechanical brake (EMB)according to an embodiment of the present invention. FIG. 2 is a planview of the EMB according to an embodiment of the present invention.FIG. 3 is an exploded perspective view of the EMB according to anembodiment of the present invention. FIG. 4 is a perspective view of adifferential gear unit of the EMB according to an embodiment of thepresent invention. FIG. 5 is a cross-sectional view taken along lineA-A′ of FIG. 1. FIG. 6 is a cross-sectional view illustrating a state inwhich a first braking unit and a second braking unit are operated by adriving unit in FIG. 5.

As illustrated in FIGS. 1 through 6, an electro-mechanical brake (EMB)according to an embodiment of the present invention includes a drivingunit 10, a differential gear unit 20, a first pad 31, a second pad 32, afirst braking unit 40, and a second braking unit 50.

The driving unit 10 generates rotational force by power selectivelyapplied as a user operates a brake pedal.

In the present embodiment, the driving unit 10 is configured as adriving motor including a driving gear 11 coupled to a rotational shaft.

According to circumstances, the driving unit 10 may further include adecelerator coupled to the driving gear 11.

The differential gear unit 20 is connected to the driving unit 10 androtate by rotational force from the driving unit 10.

The differential gear unit 20 includes a ring gear 21, a differentialcase 22, a first shaft 23, a second shaft 24, a side gear 25, adifferential pinion 26, and a first driven gear 27.

The ring gear 21 is engaged with the driving gear 11 so as to rotate.

The differential case 21 has a channel (“⊂”) shape and both ends thereofare integrally coupled to one side of the ring gear 21.

Thus, the differential case 22 is rotated together with the ring gear21.

An empty space is formed between the differential case 22 and the ringgear 21, in which the side gear 25 and the differential pinion 26 areinsertedly disposed.

The first shaft 23 is installed to penetrate through the differentialcase 22.

The second shaft 24 is installed to penetrate through the ring gear 21and is aligned with the first shaft 23.

The side gear 25 is formed as a pair of side gears disposed to face eachother within the differential case 22, and coupled to one end of thefirst shaft 23 and the other end of the second shaft 24, respectively.

The differential pinion 26 is formed as a pair of differential pinionsdisposed to face each other within the differential case 22 and disposedto be engaged with the side gears 25 perpendicularly.

The first driven gear 27 is coupled to one end of the second shaft 24.

The foregoing differential gear unit 20 has a structure identical tothat of a general differential gear device and an operation thereof isalso identical to that of the general differential gear device, andthus, descriptions of the operation of the differential gear unit 20will be omitted.

When the driving unit 10 rotates, the ring gear 21 and the differentialcase 22 of the differential gear unit 20 are rotated by rotational forceof the driving unit 10, and accordingly, the first shaft 23 and thesecond shaft 24 disposed in a line to form rotational shafts are rotatedin the same direction.

A first pad 31 is disposed on one side of a brake disk 30, and thesecond pad 32 is disposed on the other side of the brake disk 30.

The first braking unit 40 is connected to the first shaft 23 in one endthereof and connected to the first pad 31 in the other end thereof.

According to a rotation of the first shaft 23, the first braking unit 40enables the first pad 31 to be moved in a direction toward one side ofthe disk 30 so as to be brought into contact therewith, thus generatingbraking force in the disk 30.

In the present embodiment, the first braking unit 40 is disposed in adirection parallel to the first shaft 23 and installed to have a lengthvaried in a length direction of the first shaft 23 according to arotation of the first shaft 23.

To this end, the first braking unit 40 includes a first screw unit 42and a first nut unit 43.

The first screw unit 42 is connected to the first shaft 23 in one endthereof and has a thread formed on an outer circumferential surface ofthe other end thereof.

As in the present embodiment, the first screw unit 42 may be integrallyconnected to the first shaft 23 and may be rotated together with thefirst shaft 23 according to a rotation of the first shaft 23.

The first nut unit 43 is screw-coupled with the first screw unit 42, andconnected to the first pad 31.

Thus, according to a rotation of the first screw unit 42 by the firstshaft 23, the first nut unit 43 is linearly moved, and accordingly, thefirst pad 31 coupled to the first nut unit 43 is linearly moved in adirection toward the disk 30.

The second braking unit 50 is connected to the second shaft 24 in oneend thereof and connected to the second pad 32 in the other end thereof.

The second braking unit moves the second pad 32 in a direction towardthe other side of the disk 30 and make the second pad 32 brought intocontact therewith, thus generating braking force on the disk 30.

In the present embodiment, the second braking unit 50 is disposed in adirection parallel to the second shaft 24 and installed such that alength thereof is varied in a length direction of the second shaft 24according to a rotation of the second shaft 24.

To this end, the second braking unit 50 includes a second driven gear51, a second screw unit 52, and a second nut unit 53.

The second driven gear 51 is engaged with the first driven gear 27coupled to the second shaft 24, connecting the second braking unit 50 tothe second shaft 24.

The second screw unit 52 is coupled to the second driven gear 51 in oneend and has a thread formed on an outer circumferential surface on theother end thereof.

The second screw unit 52 rotates together with the second shaft 22 bythe first driven gear 27 and the second driven gear 51 when the secondshaft 24 rotates.

The second nut unit 53 is screw-coupled to the second screw unit 52 andconnected to the second pad 32 by means of the caliper 35.

Thus, the second nut unit 53 linearly moves according to a rotation ofthe second screw unit 52 by the second shaft 24, and accordingly, thesecond pad 32 coupled to the second nut unit 53 linearly moves in adirection toward the disk 30.

Here, the first pad 31 and the second pad 32 are simultaneously broughtinto contact with the disk 30 according to operations of the firstbraking unit 40 and the second braking unit 50 based on a rotation ofthe differential gear unit 20.

In the drawing, the caliper 35 is briefly illustrated.

Hereinafter, an operational process of the present invention having theforegoing configuration will be described.

When the user does not step on the brake pedal, the first pad 31 and thesecond pad 32 are spaced apart from the disk as illustrated in FIG. 5.

In this state, when the user steps on the brake pedal, power is appliedto the driving unit 10 and the driving gear 11 rotates.

As the driving gear 11 rotates, the differential gear unit 20 engagedwith the driving gear 11 is also rotated.

In detail, the ring gear 21 engaged with the driven gear 11 is rotated,the differential case 22 integrally coupled to the ring gear 21 isrotated, and accordingly, the side gear 25, the differential pinion 26,the first shaft 23, the second shaft 24, and the first driven gear 27are also rotated together.

Here, the first shaft 23 and the second shaft 24 are rotated in the samedirection.

As the first shaft 23 is rotated, the first screw unit 42 coupled to thefirst shaft 23 is also rotated, and accordingly, the first nut unit 43moves the first pad 31 in a direction toward the disk 30 to make thefirst pad 31 brought into contact with the disk 30, thus generatingbraking force, as illustrated in FIG. 6.

Namely, the first braking unit 40 has a length increased sufficient tomake the first pad 31 clamped to the disk 30.

As the second shaft 24 rotates, the first driven gear 27 and the seconddriven gear 51 coupled to the second shaft 24 are rotated.

Also, as illustrated in FIG. 6, the second screw unit 52 coupled to thesecond driven gear 51 is rotated, and accordingly, the second nut unit53 moves the second pad 32 in a direction toward the disk 30 to make thesecond pad 32 brought into contact with the disk 30, thus generatingbraking force.

Here, threads of the first screw unit 42 and the second screw unit 52are formed in the same direction.

As the first driven gear 27 and the second driven gear 51 are engaged,the second screw unit 52 rotates in a direction opposite a direction ofthe first screw unit 42.

Thus, unlike the first braking unit 40, the second braking unit 50 isshortened in length, allowing the second pad 32 to be clamped to thedisk 30.

Alternatively, a direction change gear (not shown) may be disposedbetween the first driven gear 27 and the second driven gear 51.

Here, the threads of first screw unit 42 and the second screw unit 52may be formed in the opposite directions.

Also, the second screw unit 52 is rotated in a direction identical tothat of the first screw unit 42 by the direction change gear disposedbetween the first driven gear 27 and the second driven gear 51.

Thus, even though the first screw unit 42 and the second screw unit 52are rotated in the same direction, since the threads thereof are formedin the opposite directions, the second braking unit 50 is shortened inlength, allowing the second pad 32 to be clamped to the disk 30, unlikethe first braking unit 40.

Meanwhile, when any one of the first braking unit 40 and the secondbraking unit 50 are overloaded, greater rotational force is transmittedto the other braking unit.

Thus, braking force may substantially simultaneously be generated in thefirst braking unit and the second braking unit 50.

This is the function provided by the differential gear device, and inthe present invention, the differential gear device is configured toprevent wear variations between the brake pads and obtain reliability ofa response speed of a brake.

Thus, in the present invention, a single power source (motor) and thedifferential gear unit 20 are configured as a power transmission device,whereby the outer surface and the inner surface of the disk 30 aresubstantially simultaneously clamped to minimize wear variations betweenthe first pad 31 (inner pad) and the second pad (outer pad) and breakingat the initial braking operation before the second pad 32 (outer pad) isclamped can be enhanced.

The EMB according to the present invention is not limited to theabove-described embodiments, and may be corrected and modified withinthe technical scope obvious to those skilled in the art.

The EMB according to the present invention as described above has thefollowing advantages.

Since the first pad (inner pad) and the second pad (outer pad) disposedon both sides of the disk are substantially simultaneously clamped tothe disk by the driving unit and the differential gear unit, wearvariations of both sides of the disk can be minimized and braking forceand responsiveness in a braking operation can be enhanced.

Also, since the differential gear unit is configured as a powertransmission source, when any one of the first braking unit and thesecond braking unit is first loaded, a greater amount of rotationalforce is transmitted to the other braking unit, whereby the firstbraking unit and the second braking unit can be substantiallysimultaneously driven together.

In addition, since the EMB is implemented with a relatively simplestructure, excellent productivity and assembly characteristics can beobtained.

A number of exemplary embodiments have been described above.Nevertheless, it will be understood that various modifications may bemade. For example, suitable results may be achieved if the describedtechniques are performed in a different order and/or if components in adescribed system, architecture, device, or circuit are combined in adifferent manner and/or replaced or supplemented by other components ortheir equivalents. Accordingly, other implementations are within thescope of the following claims.

What is claimed is:
 1. An electro-mechanical brake (EMB) comprising: adriving unit configured to generate rotational force by powerselectively applied as a user operates a brake pedal; a differentialgear unit connected to the driving unit and including a first shaft anda second shaft disposed to be aligned to form rotational shafts androtate in the same direction by rotational force from the driving unit;a first pad disposed on one side of a brake disk; a second pad disposedon the other side of the disk; a first braking unit connected to thefirst shaft in one end thereof and connected to the first pad in theother end thereof and configured to enable the first pad to be broughtinto contact with one side of the disk according to a rotation of thefirst shaft to generate braking force; and a second braking unitconnected to the second shaft in one end thereof and connected to thesecond pad in the other end thereof and configured to enable the secondpad to be brought into contact with the other side of the disk accordingto a rotation of the second shaft to generate braking force, wherein thefirst braking unit moves in a first plane and the second braking unitmoves in a second plane different from the first plane, wherein thefirst braking unit is disposed in a direction parallel to the firstshaft and varied in length in a length direction of the first shaftaccording to a rotation of the first shaft, wherein the second brakingunit is disposed in a direction parallel to the second shaft and variedin length in a length direction of the second shaft according to arotation of the second shaft, wherein the first braking unit, with alength increasing, moves the first pad in the direction toward the disk,and the second braking unit, with a length decreasing, moves the secondpad in the direction toward the disk.
 2. The electro-mechanical brake ofclaim 1, wherein the driving unit is configured as a driving motorhaving a driving gear coupled to a rotational shaft.
 3. Theelectro-mechanical brake of claim 2, wherein the differential gear unitcomprises: a ring gear rotated in mesh with the driving gear; adifferential case coupled to one side of the ring gear and rotatedtogether with the ring gear; the first shaft penetrating through thedifferential case; the second shaft penetrating through the ring gearand aligned with the first shaft; a pair of side gears disposed to faceeach other and coupled to one end of the first shaft and the other endof the second shaft, respectively, within the differential case; and apair of differential pinions engaged with the pair of side gearsperpendicularly and disposed to face each other within the differentialcase.
 4. The electro-mechanical brake of claim 3, further comprising afirst driven gear coupled to one end of the second shaft.
 5. Theelectro-mechanical brake of claim 3, wherein when the driving motorrotates, the first shaft and the second shaft are rotated in the samedirection according to rotations of the ring gear and the differentialcase.
 6. The electro-mechanical brake of claim 1, wherein the firstbraking unit comprises: a first screw unit connected to the first shaftin one end thereof and having a thread formed on an outercircumferential surface of the other end thereof; and a first nut unitscrew-coupled to the first screw unit and connected to the first pad,wherein the first pad coupled to the first nut unit linearly moves in adirection toward the disk according to a rotation of the first screwunit by the first shaft.
 7. The electro-mechanical brake of claim 1,wherein the second braking unit comprises: a second driven gear engagedwith the first driven gear coupled to the second shaft so as to beconnected to the second shaft; a second screw unit coupled to the seconddriven gear in one end thereof and having a thread formed on an outercircumferential surface of the other end thereof; and a second nut unitscrew-coupled to the second screw unit and connected to the second padby a caliper, wherein the second pad coupled to the second nut unitlinearly moves in a direction toward the disk according to a rotation ofthe second screw unit by the second shaft.
 8. The electro-mechanicalbrake of claim 1, wherein the first pad and the second pad aresimultaneously be brought into contact with the disk according tooperations of the first braking unit and the second braking unit basedon a rotation of the differential gear unit.
 9. The electro-mechanicalbrake of claim 2, wherein the first pad and the second pad aresimultaneously be brought into contact with the disk according tooperations of the first braking unit and the second braking unit basedon a rotation of the differential gear unit.
 10. The electro-mechanicalbrake of claim 1, wherein the first pad and the second pad aresimultaneously be brought into contact with the disk according tooperations of the first braking unit and the second braking unit basedon a rotation of the differential gear unit.
 11. The electro-mechanicalbrake of claim 7, wherein the threads of the first screw unit and thesecond screw unit are formed in the same direction.
 12. Theelectro-mechanical brake of claim 7, wherein a direction change gear isdisposed between the first driven gear and the second driven gear, andthe threads of the first screw unit and the second screw unit are formedin the opposite directions.